Knee airbag

ABSTRACT

A knee airbag apparatus includes a front panel configured to face toward an occupant when the knee airbag deploys and a rear panel configured to face toward an instrument panel when the knee airbag deploys. The rear panel is joined to the front panel to form an inflatable knee cushion configured to inflate to protect an occupant&#39;s knees during a crash event. The knee airbag further includes at least one internal tether extending between the front and rear panels. The internal tether is attached to the front panel at a front panel attachment location offset from a rear panel attachment location. The knee airbag further includes an external tether attached at one end to the front panel, and at a second end at the knee airbag housing.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application claims priority from Provisional Application U.S.Application 60/996,148, filed Nov. 2, 2007, incorporated herein byreference in its entirety.

BACKGROUND

The present disclosure relates generally to the field of vehicleairbags. More particularly, the present disclosure relates to the fieldof knee airbags with improved deployment.

Airbags are provided in vehicles to protect occupants from injury in theevent of a vehicle crash. Knee airbags in particular can help preventinjury to an occupant's legs by preventing the legs from hitting thedash or an instrument panel in the event of a crash.

SUMMARY

One exemplary embodiment provides a knee airbag apparatus. The kneeairbag apparatus comprises a front panel configured to face toward anoccupant when the knee airbag deploys, and a rear panel configured toface toward an instrument panel when the knee airbag deploys. The rearpanel is joined to the front panel to form an inflatable knee cushionconfigured to inflate to protect an occupant's knees during a crashevent. The knee airbag apparatus includes a first internal tetherextending between the front and rear panels. The first internal tetheris attached to the front panel at a front panel attachment locationoffset from a rear panel attachment location.

Another exemplary embodiment provides method of forming a knee airbag.The method comprises: joining a front panel to a rear panel to form aknee cushion; laying the knee cushion flat such that the rear panel ison top of the front panel; and folding the knee cushion. Folding of theknee cushion includes rolling the knee cushion beginning at a top end ofthe knee cushion toward a bottom end of the knee cushion with a mountingbracket. After rolling the knee cushion toward the bottom end, the kneecushion is folded back towards the front end in a Z-type fold.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory only,and are not restrictive of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentdisclosure will become apparent from the following description, appendedclaims, and the accompanying exemplary embodiments shown in thedrawings, which are briefly described below.

FIG. 1 is a perspective view of the interior of a vehicle illustrating alocation of a knee airbag assembly according to an exemplary embodiment.

FIG. 2 is a side view of a vehicle interior showing a knee airbag in astowed configuration and a trajectory of the knee airbag according to anexemplary embodiment.

FIG. 3 is a side view of a vehicle interior showing a deploying kneeairbag illustrating the external tether before the tether rupturesaccording to an exemplary embodiment.

FIG. 4 is a side view of a vehicle interior showing a deployed kneeairbag illustrating the relationship between chamber and thecushion/housing according to an exemplary embodiment.

FIG. 5 is a front view of a flattened, uninflated knee airbag cushionillustrating a trapezoidal shaped external tether according to anexemplary embodiment.

FIG. 6 is a front view of a flattened, uninflated knee airbag cushionillustrating the trapezoidal shaped external tether wrapped around theairbag cushion and coupled to a housing according to an exemplaryembodiment.

FIG. 7A is a side view of a partially assembled knee airbag cushionillustrating internal tethers according to an exemplary embodiment.

FIG. 7B is a side view of a knee airbag cushion including a plurality ofoffset internal tethers according to an exemplary embodiment.

FIG. 7C is a side view of a known knee airbag cushion including aplurality of parallel tethers according to prior art.

FIG. 8 is a side view of a process for the folding of a knee airbagaccording to an exemplary embodiment.

FIGS. 9A-9F are front views of an external tether for a knee airbagaccording to other exemplary embodiments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Airbags may be provided in a vehicle to protect the occupants of thevehicle in a collision. The airbags generally comprise a fabric bag orcushion that is inflated with gas from a gas generator (e.g., apyrotechnic gas generator). The airbags are often stored out of sight,such as behind trim pieces, and are inflated to occupy the space betweenan occupant of the vehicle and a structure that may injure the occupantin a collision (e.g., a steering wheel, the vehicle dash, instrumentpanel, doors, windows, etc.)

Knee airbags are provided in vehicles to help prevent an occupant's legsfrom hitting a dash or instrument panel in the event of a vehiclecollision. However, the force of a still-inflating airbag may injure theoccupant, especially in an out-of-position (OOP) situation, such as ifthe occupant is not wearing a safety belt and is too close to the dashwhen the airbag deploys. In order to decrease possible injury to anoccupant's legs occurring from the force of the deploying airbag, it isdesirable to minimize the interaction between a deploying airbag cushionand occupants' legs. In an embodiment, the trajectory of the airbag isin a generally vertical direction. With the vertical trajectory, theairbag deploys upward, following the instrument panel surface, ratherthan toward the occupant's legs, thus decreasing the interaction betweenthe deploying airbag cushion and the occupant's legs.

Referring to FIG. 1, the location of a knee airbag assembly 20 in theinterior of a vehicle 10 is shown according to an exemplary embodiment.The airbag assembly 20 is stored and concealed in a housing 12 (e.g.,recess, socket, compartment, etc.) in a dash panel 14. According to oneexemplary embodiment, the dash panel 14 may be below an instrument panel(e.g., for a driver's side knee airbag assembly). Thus, the knee airbagassembly 20 may be a driver or passenger side airbag assembly.

Referring now to FIGS. 2-4, the knee airbag assembly 20 is shownaccording to an exemplary embodiment. The knee airbag assembly 20includes an airbag cushion 30, that remains folded in the housing 12awaiting deployment, and an inflator 22 to inflate the airbag cushion 30once a collision is sensed. The inflator 22 is, for example, aconventional pyrotechnic gas generator, or any other suitable type ofinflator. The inflator 22 is coupled to the airbag cushion 30 with adiffuser bracket 24. When a collision is detected, the inflator 22generates a gas that fills the airbag cushion 30. As the airbag cushion30 is filled, the cushion 30 expands to deploy out of the housing 12 andbetween the occupant 16 and the vehicle dash panel 14.

Referring to FIGS. 5-6, a knee airbag cushion 30 is shown in more detailaccording to an exemplary embodiment. The cushion 30 is formed fromseveral panels of a fabric such as nylon that are sewn together. Airbagcushions such as cushion 30 are generally formed with at least a frontpanel 32 and a rear panel 34 that are coupled together at a first seam33 that extends generally around the periphery of the cushion 30. Whenthe airbag cushion 30 is deployed, the rear panel 34 is proximate to thedash panel 14 with the front panel 32 remote from the dash panel 14,proximate to the occupant 16. An opening in the cushion 30 is alignedwith the inflator 22. A portion of the inflator 22 extends through anopening 36 in the rear panel 34 so that gas generated by the inflator 22can enter the cushion 30. The cushion 30 is trapped between the inflator22 and the bracket 24. The bracket 24 extends through openings 38 in therear panel 34 and is coupled to the inflator 22 to hold the cushion 30in place.

The cushion 30 further includes an external tether 40 to help controlthe trajectory of airbag cushion 30 during deployment. Morespecifically, the tether 40 is configured to direct the airbag cushion30 to deploy in a generally vertical direction, along the dash panel 14rather than in a horizontal direction, towards the legs of the occupant16. The tether 40 may be formed from the same material as the frontpanel 32 and the rear panel 34 such as a nylon fabric, or any othersuitable type of material.

The external tether 40 is coupled to at least one of the front panel 32or the rear panel. The tether 40 is releasably coupled to cushion 30such that it may rip or tear away from the cushion 30 during thedeployment of the cushion 30. This releasable coupling is provided alonga relatively wide area so that the external tether 40 may moreeffectively compensate for lateral (e.g., left, right, center)variations in deployment speed of the cushion 30.

In an exemplary embodiment, the external tether 40 is a trapezoidalfabric panel with a wide end 42 and a narrow end 46. The narrow end 46may have one or more openings 48 that are similar to the openings 36 and38 in the rear panel 34. The openings 48 are aligned with the openings36 and 38 in the rear panel 34 such that the narrow end 46 of theexternal tether 40 may be trapped between the inflator 22 and thebracket 24 along with the rear panel 34 to hold the external tether 40in place (e.g., generally coupled to the inflator 22 and the bracket24). The wide end 42 of the external tether 40 is coupled to the frontpanel 32. According to an exemplary embodiment, the wide end 42 isstitched to the front panel 32 at a second seam 43. The wide end 42 isfirst sewn to the cushion 30 and then the external tether 40 is wrappedaround the cushion 30 so that the narrow end 46 may be coupled to thebracket 24, a fixed part of the knee cushion 30 near the housing, or thehousing itself.

When wrapped around the cushion 30, the external tether 40 constrainsthe cushion 30 so that it may not fully inflate (see FIG. 3). Theconstraining of the cushion during deployment causes it to first deployin a lateral direction (e.g., out to the side) and facilitates thedeployment of the cushion 30 along a generally vertical trajectory. Amultitude of frangible regions or break points 44 are provided proximateto the second seam 43 along which the external tether 40 may be torn orotherwise ruptured to allow the cushion 30 to fully deploy. While theexternal tether 40 is shown with three break points 44 in FIGS. 5 and 6,according to other exemplary embodiments, the external tether 50 mayinclude more or fewer break points 44.

According to an exemplary embodiment, as shown in FIGS. 5, 6, and 9B,the break points 44 are provided in the form of narrow frangibleportions. According to other exemplary embodiments, the break points 44may be other structures (i.e., tear tabs, detachable stitches, etc.). Bybeing located proximate to the wide end 42, the break points 44 arearranged over a wide range of areas. The gas generated by the inflator22 may apply an uneven outward force on the cushion 30 causing an unevendeployment speed across the width of the cushion. The break points 44can have a determined strength pre-set to control deployment trajectoryof cushion 30 and balance the left-center-right speed of cushion 30.

Referring to FIGS. 9A-9F, external tethers 40 are shown according toseveral exemplary embodiments. For example, the break points 44 may beformed by narrow portions of the tether 40 formed by large openings (seeFIG. 9C) or may be narrow portions of the tether 40 that connect themain body of the tether 40 to tabs that are coupled to the airbagcushion at seams 43.

According to other exemplary embodiments, the break points 44 may beprovided in the form of frangible seams 47 (see FIGS. 9A, 9D, and 9F)that are configured to couple the tether 40 to the airbag cushion 30 andtear or burst during the deployment of the airbag cushion 30. Thefrangible seams 47 may be several discreet stitches provided along thewide end 42 of the tether 40 or may be a continuous stitch providedalong the wide end 42 of the tether 40.

According to another exemplary embodiment, the external tether 40 maycomprise one or more generally narrow strips that are coupled on a firstend 46 to the bracket 24 and on a second end 42 to the airbag cushion 30(see FIG. 9F). The second end 42 may be coupled to the airbag cushion ata fixed seam 43 and include break points 44 or may be coupled to theairbag cushion 30 with at frangible seam 47.

Referring now to FIGS. 7A and 7B, according to another exemplaryembodiment, an airbag cushion 30 may include one or more internaltethers 50 to help control the trajectory of airbag cushion 30 duringdeployment. More specifically, the tethers 50 are configured to directthe airbag cushion 30 to deploy in a generally vertical direction, alongthe dash panel 14 rather than in a horizontal direction, towards thelegs of the occupant 16. The tethers 50 may be formed from the samematerial as the front panel 32 and the rear panel 34 such as a nylonfabric.

Internal tethers 50 are shifted between front and rear panel to pull thecushion 30 upward against the dash panel 14 surface, improvingdeployment trajectory and reducing the interaction of the cushion withthe occupant's legs. The distance between the point at which theinternal tethers 50 are coupled to the rear panel 34 and the bracket 24is less than the distance between the point at which the internaltethers 50 are coupled to the front panel 32 and the bracket 24 suchthat the tethers 50 form an acute angle (Θ) with the rear panel 34. Theangle (Θ) is determined by the length of the internal tether 50 and theoffset between the points at which the internal tether 50 is coupled tothe rear panel 34 and the front panel 32. The difference in distance ofeach end of the tethers 50 to the bracket 24 urges the rear panel 34 tocontract and be pulled upward. This pulling force helps to control thetrajectory of the airbag cushion 30. According to an exemplaryembodiment, at least one of the internal tethers 50 has an offset in arange of approximately 15 to 60 mm; or more specifically in a range of20 to 50 mm, or more specifically of approximately 40 mm. For example, adistance from a bottom seam 33 to the first tether 50 in the first panel32 is about 40 mm different from a distance from a bottom seam 33 to thefirst tether 50 on the rear panel 34. According to an exemplaryembodiment, the angle (Θ) formed between the internal tethers 50 and therear panel 34 is between five to 85 degrees, or in a range of 9 to 85degrees, or more specifically in a range of 9 degrees to 81 degrees.According to a preferred embodiment, the angle (Θ) formed between theinternal tethers 50 and the rear panel 34 is between 35 degrees and 80degrees.

The internal tethers 50 and the geometry of the cushion 30 areconfigured to facilitate the generally vertical deployment of the kneeairbag cushion 30 along the surface of the dash panel 14. An upwardcushion 30 along the dash panel 14 rather than towards the occupant'slegs provides decreased interaction between the airbag cushion 30 andthe occupant's legs.

As shown in FIG. 4, the distance 60 from the center line of the bracket24 to the seam 33 between the front panel 32 and the rear panel 34 isgreater than the distance 62 between the center line of the bracket 24and the lower edge 13 of the housing 12. The cushion 30 bears againstthe lower edge 13 of the housing 12, which adds support to the cushion30 and helps to support it in a generally vertical orientation (e.g.,along the surface of the dash panel 14).

As shown best in FIGS. 7A and 7B, the front panel 32 extends longer thanthe rear panel 34 during inflation. The difference in extended lengthsurges the cushion 30 to curve convexly outward (e.g., toward theoccupant 16) and more closely follow the contour of the dash panel 14.The offset internal tethers 50 allow the front panel 32 to extendfarther upward such that the cushion 30 inflates upward and follows thedash panel 14 as opposed to extending more toward an occupant. Thepanels 32, 34 can have the same length prior to inflation or differentlengths. However, the offset tethers 50 (in conjunction with theexternal tether 40) is what creates the inflation shape of the kneeairbag cushion 30. FIG. 7C illustrates a conventional knee airbag thatincludes parallel internal tethers (no offset angle, or offset angle isequal to 90 degrees).

Referring now to FIG. 8, a method of folding the knee airbag cushion 30is shown. The airbag cushion 30 is folded to better control trajectoryand deployment of the cushion 30. The cushion is laid out flat inuninflated state with the rear panel 34 facing upward and the wide end42 an external tether 40 coupled to the front panel 34. The sides of theknee cushion 30 may be tucked into the cushion to reduce the width ofthe cushion 30.

The end of the cushion 30 remote from the bracket 24 (e.g., the top ofthe cushion 30) are then folded back on itself a number of times.According to an exemplary embodiment, the cushion 30 is folded back fivetimes. According to other exemplary embodiments, the cushion 30 may befolded back more or fewer times, for example, depending on the length ofthe cushion 30 and the desired size of the stowed cushion 30. The narrowend 46 of the external tether 40 is then coupled to the bracket 24. Thefinal fold of the cushion 30 and the tether 40 is a half fold in theopposite direction (e.g., a half “Z” fold). Additional “Z” folds may beused. When the cushion 30 and the tether 40 are folded, they are held inthe housing 12 proximate to the inflator 22, with the bracket 24 coupledto the inflator 22.

It should be recognized that the front and rear panels may be formed ofone single sheet that is folded over and sewn together to from the kneecushion. Alternatively, the knee cushion 30 may be formed from anysuitable number of sheets (panels).

It is important to note that the construction and arrangement of theattachment method of an airbag inflator to an airbag module housing asshown in the various exemplary embodiments are illustrative only.Although only a few embodiments have been described in detail in thisdisclosure, those skilled in the art who review this disclosure willreadily appreciate that many modifications are possible (e.g.,variations in sizes, dimensions, structures, shapes and proportions ofthe various elements, values of parameters, mounting arrangements, useof materials, colors, orientations, etc.) without materially departingfrom the novel teachings and advantages of the subject matter recited inthe description. For example, elements shown as integrally formed may beconstructed of multiple parts or elements, the position of the elementsmay be reversed or otherwise varied, and the nature or number ofdiscrete elements or positions may be altered or varied. Othersubstitutions, modifications, changes and omissions may be made in thedesign, operating conditions and arrangement of the exemplaryembodiments.

1. A knee airbag apparatus, comprising: a front panel configured to facetoward an occupant when the knee airbag deploys: a rear panel configuredto face toward an instrument panel when the knee airbag deploys, therear panel joined to the front panel to form an inflatable knee cushionconfigured to inflate to protect an occupant's knees during a crashevent, the front and rear panels being joined at a bottom perimeterseam; a first internal tether extending between the front and rearpanels, the first internal tether attached to the front panel at a frontpanel attachment location and attached to the rear panel at a rear panelattachment location; and an external tether, wherein a first end of theexternal tether is attached to the front panel, and a second end of theexternal tether is fixed to a housing member, and wherein a distancebetween the rear panel attachment location and the bottom perimeter seamis less than a distance between the front panel attachment location andthe bottom perimeter seam when the airbag is inflated.
 2. The kneeairbag apparatus of claim 1, further comprising a second internal tetherextending between the front and rear panels, the second internal tetherbeing attached to the front panel at a second front panel attachmentlocation and attached to the rear panel at a second rear panelattachment location, wherein a distance between the second rear panelattachment location and the bottom perimeter seam is less than adistance between the second front panel attachment location and thebottom perimeter seam when the airbag is inflated.
 3. The knee airbagapparatus of claim 2, wherein the second internal tether is parallel tothe first internal tether.
 4. The knee airbag apparatus of claim 2,wherein an offset angle between the front panel attachment location andthe rear panel attachment location of the first internal tether isdifferent from an offset angle between the second front panel attachmentlocation and the second rear panel attachment location of the secondinternal tether.
 5. The knee airbag apparatus of claim 1, wherein anoffset angle between the front panel attachment location and the rearpanel attachment location of the first internal tether is less than 90degrees.
 6. The knee airbag apparatus of claim 5, wherein the offsetangle is in a range of five to 85 degrees.
 7. The knee airbag apparatusof claim 2, wherein the first and second internal tethers are configuredto pull the knee cushion upward against the instrument panel.
 8. Theknee airbag apparatus of claim 1, wherein the distance between the rearpanel attachment location and the bottom perimeter seam is less than thedistance between the front panel attachment location and the bottomperimeter seam by approximately 15 to 60 mm.
 9. The knee airbagapparatus of claim 1, wherein the first internal tether has an offsetbetween the front panel attachment location and the rear panelattachment location in a range of approximately 15 mm to 60 mm.
 10. Theknee airbag apparatus of claim 9, wherein the first internal tether hasan offset angle between the front panel attachment location and the rearpanel attachment location in a range of nine to 85 degrees.
 11. The kneeairbag apparatus of claim 1, wherein the external tether comprises atrapezoidal shape.
 12. The knee airbag apparatus of claim 1, wherein theexternal tether includes at least one frangible portion.
 13. The kneeairbag apparatus of claim 1, wherein the first end of the externaltether is releasably attached to the front panel.
 14. The knee airbagapparatus of claim 1, wherein the first end or a middle portion of theexternal tether includes a frangible portion configured to release theexternal tether from the knee airbag.
 15. The knee airbag apparatus ofclaim 1, further comprising a bracket configured to mount the kneeairbag in a housing, the housing located in an instrument panel of avehicle.
 16. The knee airbag apparatus of claim 15, wherein a firstdistance from a center line of the bracket to a seam connecting thefront and rear panels at a bottom of the knee cushion is greater than asecond distance from the center line of the bracket to a lower edge ofthe housing.
 17. The knee airbag apparatus of claim 1, wherein the frontand rear panels are formed of a single sheet.